Originally posted by Smokinspeeds
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The F20B pistons will protrude from the bore .020" which is exactly what it comes out of the bore on a factory F20B. That engine still uses a .026" head gasket but you could go thicker if you wanted. You'd also need to either get aftermarket F22A rods or have your OEM rods rebushed for floating pins.
I actually have two sets of them and was considering listing one on eBay.My Members' Ride Thread - It's a marathon build, not a sprint. But keep me honest on the update frequency!
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Originally posted by Jarrett View PostThe F20B pistons will protrude from the bore .020" which is exactly what it comes out of the bore on a factory F20B. That engine still uses a .026" head gasket but you could go thicker if you wanted. You'd also need to either get aftermarket F22A rods or have your OEM rods rebushed for floating pins.
I actually have two sets of them and was considering listing one on eBay.
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They would come with pins and wire locks. But again, you'd be spending around $60 at the machine shop getting the rods rebushed. I also forgot to mention tht th aftermarket F22/H23 rods are usually 141.75-142mm instead of 141.5mm. At least that's what they're advertised. You can run a .051" headgasket from one of the cheaper companies like Evergreen and be okay. But tuning will be critical. I should also emphasize that tuning will be critical regardless. We're talking pretty dang high compression with these pistons being stroked an extra 7mm in the cylinders and squishing it the mixture into a smaller combustion chamber.My Members' Ride Thread - It's a marathon build, not a sprint. But keep me honest on the update frequency!
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Originally posted by Jarrett View PostThey would come with pins and wire locks. But again, you'd be spending around $60 at the machine shop getting the rods rebushed. I also forgot to mention tht th aftermarket F22/H23 rods are usually 141.75-142mm instead of 141.5mm. At least that's what they're advertised. You can run a .051" headgasket from one of the cheaper companies like Evergreen and be okay. But tuning will be critical. I should also emphasize that tuning will be critical regardless. We're talking pretty dang high compression with these pistons being stroked an extra 7mm in the cylinders and squishing it the mixture into a smaller combustion chamber.
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Your thinking is backwards on the stroke/compression issue if I'm understanding what you're saying correctly.
In this case, the F20B uses an 88mm stroke, a 145mm rod and a 31mm-tall piston with a 4.7cc dome in a 53.8cc head. This combination equates to an 11.0:1 CR.
Right off the bat you know you're putting a head on it that is 50.5cc. The smaller chamber alone would net you 11.7:1 CR. That's just theoretical, though, as no one would put a non-VTEC F22B head on an F20B block. Even if someone wanted to you'd have the exact reversal of the oil drain issues that people have to deal with when putting H22A heads on F22A blocks. But, I digress.
So now, you have to understand that an engine's compression ratio is just what it implies. It is the ratio between the volume of a cylinder/headgasket void/combustion chamber at BDC compared to the volume at TDC.
So let's change the stroke. The F22A/B uses a 95mm stroke vs. the 88mm F20B stroke. That's 7mm greater length in the cylinder the piston will be traveling down and ingesting air. Functionally, the rod will have to be changed to compensate for the overall height at TDC which is why we use the accompanying F22A/B rod along with it.
The throw of the crank (stroke/2) along with rod length between the two engines adds up to the same number. So, in essence, using the same F20B piston again will put the piston just as high out of the block at TDC using the F22A/B crankshaft and rods. So the final volume of air that will exist in the combustion chamber will be the same.
But remember, the stroke is now ingesting and additional 7mm of air. So the ratio will now increase.
In case you're wondering, this combination of an F22A with F20B pistons will yield a 12.54:1 CR. This can be brought down substantially with a thicker headgasket. The cheap eBay-bought gaskets are okay for this because they are 5-layer steel and around .051" thick. Using one of those would get you back to the 11.7:1 CR we mentioned earlier. That's plenty streetable with a good tuner and you should be able to find a set of camshafts that will compliment compression that high and behave as well.My Members' Ride Thread - It's a marathon build, not a sprint. But keep me honest on the update frequency!
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So it's been a while since anyone posted in here, are any of my fellow Texans doing anything new? Currently I'm planning on some minor maintenance (fixing an oil pan and replacing some seals in the block and head) and upgrading various suspension components. I'm installing my Innovative traction bar and here soon I'll be ordering a set of BC racing BR coilovers. following that I'll be finishing up piecing together all of the energy suspension bushings and installing everything at once and then getting aligned.
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I'm still working on getting my '91 up to snuff. I'm planning on totally replacing all of the suspension, starting with the front. I'm just waiting on tie rods and I can get started.
After that I'll do the rear, then start working on cosmetics on the inside, like replacing the upholstery and getting my center console lights to work.
Isn't it nice not having to worry about rust like the guys up north?My '91 LX build. Bought September 2017. Sold June 2020.
http://www.cb7tuner.com/vbb/showthre...r /> t=209871
Current mileage: 399450 5/18/2020
My '92 LX build. Bought Novemeber 2019. http://www.cb7tuner.com/vbb/showthre...91#post3293791
Current mileage: 422679 11/21/19
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Originally posted by wtfisafleek View PostI'm still working on getting my '91 up to snuff. I'm planning on totally replacing all of the suspension, starting with the front. I'm just waiting on tie rods and I can get started.
After that I'll do the rear, then start working on cosmetics on the inside, like replacing the upholstery and getting my center console lights to work.
Isn't it nice not having to worry about rust like the guys up north?
The good thing about doing the suspension is that you can safely do it in parts (so long as you bilaterally upgrade components, do the left and right side of any given component). The coilovers will be a single big upgrade done at once and then slowly I'll be replacing all of the bushings. Brakes will be next, I still have to make a decision about which direction I want to go. I have to consider if I want to stay 4x114, HOR and what I really need for brakes (and that will for the most part determine what path I take, if I feel the need for more brake pad options I'll go with the path that opens up more options in that respect).
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Bunta, where in Texas are you?My Members' Ride Thread - It's a marathon build, not a sprint. But keep me honest on the update frequency!
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